This invention relates to packaged electronic devices and, more particularly, to a package structure for a surface-mounted electronic device.
Many electrical devices are fragile and readily damaged by dust, corrosive agents, and the like. To protect the electrical devices, they are usually packaged in a protective housing. The nature of the housing is selected according to the type of electrical device being packaged and the expected service conditions.
In one approach used where the electronic device and package may be exposed to elevated temperatures in service, because of the environment or because the electronic device produces a great deal of heat, the electronic device is packaged in a ceramic housing which provides mechanical protection and, additionally, may be hermetically sealed to protect against intrusion of liquids or gases that may damage the packaged device. The package normally includes two parts, a base to which the electronic device is affixed, and a lid. To fabricate the final packaged structure, the electronic device is affixed to the base and electrical connections are made to the electronic device. The electrical connections are typically made by surface traces extending from the interior of the package to the exterior, or by vias extending through the bottom side of the base. After the electrical device is affixed to the base and electrically connected, the lid is positioned over the electronic device and affixed to the base, as by brazing or soldering.
When the electronic device itself produces a great deal of heat in operation, as in the case of power MOSFETs, the package is structured to provide a heat sink function that conducts the produced heat from the interior to the exterior of the package. An external heat sink may be affixed to the bottom of the package to aid in the removal of heat.
Although existing packages and proposed package designs are operable to some extent, there is always a need for packages that have improved convenience of use with reduced fabrication costs. Such improved packages should have good electrical performance as well as thermal performance, particularly when used to package high-power electronic devices. The present invention fulfills this need, and further provides related advantages.